1. Field of the Invention
This invention relates to devices and methods for endovascular treatment of blood vessel anomalies and, more particularly, for the implantation of vascular grafts.
2. Description of the Prior Art
Blood vessel anomalies, such as aneurysms, stenoses, etc., have been treated in the prior art through surgical procedures, wherein the diseased portion of the blood vessel may be ablated and replaced with a prosthetic member, such as shown in U.S. Pat. No. 4,938,740 to Melbin. An improvement over this technique which obviates the need for open surgery is directed to the endovascular placement of a stent-reinforced graft. The stent and graft is entered into the bloodstream from a remote puncture site, typically through the neck or femoral region, via a catheter in an unexpanded state to facilitate movement thereof through the blood vessel. The stent/graft assembly is aligned in the blood vessel using techniques known by those skilled in the art such that the assembly extends between healthy portions of the blood vessel and by-passes the blood vessel anomaly. Once properly aligned, the stent and graft are caused to expand thereby engaging axially-spaced sections of healthy blood vessel wall and defining an enclosed pathway for blood flow through the anomaly. If, for example, a graft was disposed in such a manner to by-pass an aneurysm and such aneurysm ruptured, the emplaced graft would act as a conduit to maintain a continuous flow of blood through the ruptured portion of blood vessel.
Different devices are in the prior art which allow for endovascular movement of a stent and/or graft and expansion thereof. First, devices exist adapted to selectively elongate and foreshorten a length of tubular graft material, resulting in a corresponding change in diameter of the graft, such as in U.S. Pat. No. 5,464,449 to Ryan et al. Alternatively, a stent and/or graft may be directly disposed on an expandable angioplasty balloon, as shown in U.S. Pat. No. 5,554,182 to Dinh et al. Finally, self-expanding stents and/or grafts are known in the prior art which are spring-biased or formed of temperature sensitive material. An example of this third type of prior art is found in U.S. Pat. No. 5,562,725 to Schmitt et al.
The prior art, however, has some deficiency in providing for implantation of a stent-reinforced graft. The mounting of the graft onto a stent, in addition to a control mechanism or an angioplasty balloon, results in the graft defining a relatively significant outer dimension. As is readily appreciated, due to the small dimensions of blood vessel lumens, it is desirable to keep the profile of all endovascular devices to a minimum. Also, lower profile instruments are more easily manipulated through blood vessels, than larger profile instruments especially through blood vessels which may contain accumulated plaque.
It is an object of the subject invention to provide a collapsible support for a vascular graft which allows for low-profile insertion thereof.
It is also an object of the subject application to provide a support for maintaining a graft in a semi-expanded state with sufficient space within the graft to preferably accommodate an unexpanded stent.